1. Field of the Invention
The present invention relates to a helical scanning type recording/reproducing apparatus suitably used for a video tape recorder for recording a coded sound signal in an extended end portion of a video track.
2. Description of the Prior Art
In a known helical scanning type VTR, one end portion of the track is extended to record a time-base compressed coded sound signal in a time divisional manner with the video signal. In a one-rotation, two-head VTR of this type, even if a recording density is increased by decreasing the tape speed, the quality of reproduced sounds may not be degraded. Furthermore, a two-channel sound signal (stereo or bilingual signal) can be recorded and reproduced. In addition to this, new sound signals can be after-recorded on a magnetic tape which is already recorded.
A video signal recorded portion on the tracks corresponds to half revolution (180.degree.) of the reproducing or rotary magnetic head. In order to obtain a recording portion (about 30.degree.) of the coded sound signals by extending an end portion of the video track, an angle formed by the magnetic tape partially wound around a head drum is set to be about 210.degree.. Therefore, while one of the magnetic heads scans the recording portion of the coded sound signals, the other simultaneously scans part of the video tracks. In this manner, a so-called overlap scanning is performed.
Two-channel coded sound signal sources include a stereo broadcasting signal, a bilingual broadcasting signal and an input signal from a stereo microphone. The sources also include after recording of the above-mentioned signals, two-channel recording of a monaural signal as left and right channel signals (LR), and recording of the monaural signal, either the single left or right channel.
In general, the reproducing mode is exclusively determined. For example, a reproduced signal is produced upon an assumption that first and second channels are defined as left (L) and right (R) channels, respectively. Another case may also be assumed that (L+R) and (L-R) signals are recorded in the first and second channels, respectively. After performing predetermined operations, the L and R signals are reproduced at the left and right channels, respectively.
In the latter case, a manual switch is arranged to select one of bilingual broadcasts or one of the monaural and stereo modes. In a TV receiver, a pilot signal is detected from a multiplex sound signal, thereby providing automatic switching. However, when the sound signal is recorded as a coded sound signal in the VTR, the pilot signal is lost. As a result, automatic switching cannot be performed.
For example, assume that the recording/reproducing apparatus has a function that the (L+R) and (L-R) signals are recorded using two channels and the predetermined operations are performed to produce the L and R channels respectively to the channels. When the tape on which the L and R signals from a stereo microphone in two channels is played back, unnatural sounds are produced, resulting in inconvenience.